Posts Tagged 'Strength'

In contrast to the pretty and placid G. playtsoma, today I have a photo and video of one of the meanest mantis shrimps I have encountered. Gonodactylus chiragra occurs in the same intertidal reef flats as G. playtsoma, but its temperament is the polar opposite. It hits hard and often.

You lookin' at me?

Its coloration is a mottled brownish-yellow-green on creme; except for bright orange and yellow accents on the antennae, mouthparts, and walking legs.

Here is a quick video of G. chiragra, whalloping the wall of its aquarium; attempting to hammer my finger (off-screen). It plays at regular speed and then at one-tenth speed (the slow-mo is much more impressive and/or comical, in my opinion).

Thomas Endlein, a zoologist at Cambridge University, recently won the Biotechnology and Biological Sciences Research Council photography prize with this picture (left). It depicts an Asian weaver ant, Oecophylla smaragdina (Hymenoptera), hefting a 500 mg weight, equaling to about 100 times the weight of the ant. It comes as no surprise that ants are capable of great feats of strength; we often hear about ants lifting “X-hundred” times their body weight. What is astonishing about this photo, however, is that the ant is able to lift 100 times its weight whilst suspending itself upside down on a smooth, glass-like surface. How is it holding on?

Most insects are capable of adhesion to smooth surfaces like glass. On the tips of their legs ants and other insects have a specialized appendage called a tarsus. The tarsus includes claws for locomotion on rough terrain, as well as a flexible pad, called an arolium, for adhesion to smooth surfaces. The surface of the arloium varies within the insects: In flies and beetles it is covered with fine hairs, while on ants, bees, roaches, and grasshoppers it is a flat flexible cuticle. The arolium is coated with viscous secreted fluids allowing it to work like a wet suction cup.

As the ant plants its foot and applies an inward-dragging force on its tarsus, the arolium passively expands, increasing suction contact with the surface (see below). It is by this mechanism that ants generate the suction-adhesion forces required to carry heavy loads over smooth surfaces. This passive expansion is especially advantageous since it automatically prevents detachment in case of sudden jostling. In addition, if the ant only applies a little pressure on the arolium it does not expand as significantly, allowing the ant to move at a brisker pace when not carrying a heavy load.

Light micrographs of a weaver ant tarsus planting on a smooth surface. The arolium pad automatically expands as the appendage is dragged on the surface. Adapted from Federle, 2002

Weaver ants, like the one in the photo at top, create elaborate woven hives out of plant leaves. Their gathering routs bring them over soil, up bark, and frequently across the undersides of smooth leaves. Therefore they have evolved a tarsus the can grip with both claws and suction in order to carry their heavy payloads home.

Stomatopods, or mantis shrimp, are an exceptional order of marine crustaceans made up of over 500 species that live in a variety of benthic habitats around the world. They are aggressive predators that actively seek out their prey with an advanced suite visual and chemosensory organs. Stomatopods are immediately distinguished by a pair of enlarged raptorial appendages located ventrally, near their heads. Stomatopods use these appendages as their primary means of predation, as well as for digging in substrate, defense, and intraspecific sparring.

The appearance of the raptorial appendages varies from species to species as they are evolutionarily specialized for capturing or killing distinct prey animals. The raptorial appendages can be deployed at lightning speeds, and with tremendous force relative to the size of the stomatopods; which can range from under 2 cm to 40 cm body length. Depending on the species, these appendages can be employed to smash, spear, or grab their prey.

Here are video examples of “smasher” and “sprearer” stomatopods in action:

Odontodactylus scyllarus smashes the shells of mollusks and crustaceans.

Lysiosquillina maculata ambushes swimming fish and crustaceans, spearing them out of the water column. Click through to Youtube to see this one.

Since the 1960’s, a series of research has unraveled the speed, power, and mechanics of the stomatopod’s astonishing attack.